update_engine: add variable for DeviceQuickFixBuildToken policy

This CL makes DeviceQuickFixBuildToken policy visible in update_manager
which would be used in a follow up CL to skip applying
DeviceAutoUpdateTimeRestrictions when a quick fix build token is set.
This CL also adds quick fix token in UpdateCheckParams which is used
by UpdateAttempter to pass the token in OmahaRequestParams.

BUG=chromium:1117450
TEST=FEATURES=test emerge-${BOARD} update_engine

Change-Id: If43ad8cd2955bbeb1cbd1dcacac79742fa0a6a20
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2521189
Commit-Queue: Saurabh Nijhara <snijhara@google.com>
Tested-by: Saurabh Nijhara <snijhara@google.com>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
diff --git a/cros/omaha_request_params.cc b/cros/omaha_request_params.cc
index 0d69b24..adcfc75 100644
--- a/cros/omaha_request_params.cc
+++ b/cros/omaha_request_params.cc
@@ -122,6 +122,8 @@
 
   lts_tag_ = params.lts_tag;
 
+  autoupdate_token_ = params.quick_fix_build_token;
+
   rollback_allowed_ = params.rollback_allowed;
 
   // Set whether saving data over rollback is requested.